iOS Question WKWebview custom js

Sub wv_OverrideUrl (Url As String) As Boolean
    Log("override url")
    Log(Url)
    Dim shouldoverride=False As Boolean

    If Url.IndexOf("http")>-1 Or Url.IndexOf("mailto:")>-1 Then
        Dim App As Application
        App.OpenURL(Url)
        shouldoverride=True
    End If

    If Url.IndexOf("ReminderEnabledCheck")>-1 Then
        ReminderEnabledCheck
        shouldoverride=True
    End If
   
    If Url.IndexOf("log:")>-1 Then
        LogColor(Url.Replace("log:","").Replace("%20"," "),Colors.Yellow)
        shouldoverride=True
    End If

    If Url.IndexOf("sleeplog")>-1 Then
        Dim l As List
        l.Initialize2(Regex.Split("%5E",Url))
        If l.size=3 Then
            ShowSleepLog(l.Get(1),l.Get(2))
        Else
            ShowSleepLog(l.Get(1),"")
        End If
    End If
    Return shouldoverride
End Sub

function sendPlatformMessage(platform, message, param) {
    if (Ext.Ajax.enableExternalNotify) {
        if (platform == "Android") {
            b4a.CallSub(message,true, param);
        }
        if (platform == "iOS") {
            window.location.href = message + "^" + param;
        }
    }
}

' Create WKWebView1

    WKWebView1 = CreateWKWebView(Page1.RootPanel)
    WKWebView1.LoadUrl("file://" & File.Combine(File.DirLibrary, yourpath))

Sub CreateWKWebView (pnl As Panel) As View
    Dim conf As NativeObject
    conf = conf.Initialize("WKWebViewConfiguration").RunMethod("new", Null)
   
    Dim NativeMe As NativeObject = Me
    conf = NativeMe.RunMethod("getconfig:", Array(conf))
   
    Dim wk As NativeObject
    Dim p As NativeObject = pnl
    wk = wk.Initialize("WKWebView").RunMethod("alloc", Null)
    wk.RunMethod("initWithFrame:configuration:", Array(p.RunMethod("frame", Null), conf))
    pnl.AddView(wk, 0, 0, pnl.Width, pnl.Height)
    Return wk
End Sub

Private Sub JSCallback(body As Object)
    Log(body)
End Sub

#If OBJC
#import <Foundation/Foundation.h>

- (WKWebViewConfiguration *) getconfig: ( WKWebViewConfiguration *)config
{
       WKUserContentController* userController = [[WKUserContentController alloc]init];
       [userController addScriptMessageHandler:self name:@"callback"];
    config.userContentController = userController;
 
  return config;
}


- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message     {
if ([message.name isEqualToString:@"callback"]) {
        [self.bi raiseEvent:nil event:@"jscallback:"params:@[message.body]];
}
}
#End If

 window.webkit.messageHandlers.callback.postMessage({
        "name": "Lily",
        "breed": "Pug",
        "age": 1
    });